Method of installing liquid collection and pumping station in-situ



July 23, 1968 R. D. MITCHELL 3,393,519

METHOD OF INSTALLING LIQUID COLLECTION AND PUMPING STATION IN-SITU Filed Jan. 10, 1966 2 Sheets-Sheet 1 Fymv .D M/ rcmezl- ATTORNEY July 23, 1968 MITCHELL 3,393,519

METHOD OF INSTALLING LIQUID COLLECTION AND PUMPING STATION IN-SITU Filed. Jan. 10, 1966 2 Sheets-Sheet 2 ATTORNEYS United States Patent 3,393,519 METHOD OF INSTALLING LIQUID COLLECTION AND PUMPING STATION IN-SITU Ryan D. Mitchell, Thomasville, Ga., assignor to Davis Industries, Inc., a corporation of Georgia Filed Jan. 10, 1966, Ser. No. 519,575 3 Claims. (Cl. 61.5)

ABSTRACT OF THE DISCLOSURE A below-ground wet well for collecting and pumping sewage or the like is constructed by digging a cavity in the earth, jetting a pipe into the earth at the bottom of the cavity, constructing the walls of the wet well in the cavity with the upper end of the pipe in communication with the interior of the well and arranging an air lift pipe in the well with the lower end of the air lift dipping into the jetted-in pipe.

Disclosure This invention relates to liquid pumping apparatus and in particular to installations for collecting liquid waste and the like and for pumping the same to a higher level.

It is often necessary in systems for handling liquid waste, such as sewage or sump water to employ a wet well or the like for the collection of the waste and to provide pumping means for pumping the waste to another collection point or to a treatment plant. In a typical installation the wet well or the like comprises a below ground tank which collects the liquid waste until the liquid rises to a predetermined high level following which a pump is actuated to pump the liquid down to a predetermined low level. The present invention is concerned with improvements in the pumping means for this general type of installation and in the method by which the installation is constructed in a below-ground location.

It is one object of the present invention to provide a wet well and pump installation in which the pump is of the air lift type and in which the air lift is specially arranged relative to the well so as to produce improved pumping capacity. More specifically, the air lift is arranged in the well with its lower end dipping a substantial distance into a relatively small diameter vertical pipe which extends downwardly from the bottom of the well. The pipe is closed at its lower end thereby forming a small liquid sump which serves to maintain a substantial liquid head on the air inlet of the air lift even when the liquid level drops to the pump-off level.

It is a further object to provide a method of constructing the above-described installation in an economical manner. Broadly, the method comprises excavating a cavity in the earth of sufiicient size to hold the well container, forcing the sump pipe vertically into the earth at the bottom of the cavity, arranging the well container in the cavity above the sump pipe and lowering the air lift into the well container until its lower end dips a substantial distance into the sump pipe. An advantage in simplicity and economy can be obtained by jetting the sump pipe into the earth. In this preferred method a downwardly facing jet pipe is attached to the exterior of the sump pipe and the latter is lowered into the earth as Water is pumped into the upper end of the jet pipe to wash dirt away from the lower end of the sump pipe. When the well container is to be constructed of cement, the bottom of the container is cast around the upper end of the sump pipe after the water supply has been disconnected from the jet pipe. The latter represents a relatively small investment and may be left in the earth if desired.

It is a more specific object to provide a sump pipe and "ice jet assembly which may be employed in the construction of a Wet well or the like as described above, or which may be employed by itself as a wet well.

The invention will be further understood from the following detailed description taken with the drawings in which:

FIGURE 1 is a vertical sectional view of a wet well installation embodying the principles of the present invention;

FIGURE 2 is a vertical sectional view, on an enlarged scale, of the sump pipe and jet assembly of FIGURE 1;

FIGURE 3 is a bottom view of the assembly of FIG- URE 2;

FIGURES 4, 5 and 6 are schematic views illustrating some of the steps employed in constructing the wet well of FIGURE 1.

Referring to FIGURE 1 there is shown a sewage collection and pumping station constructed in the form of a below-ground concrete wet wall. The well is defined by a cylindrical side wall 10, a bottom wall 12 having an inclined portion 14, and a ground level top Wall 16 provided with a removable cover 18. Sewage enters the well through an inlet pipe 20 under gravity or pump flow. The mechanism for pumping sewage out of the Well includes an air lift type of pump 22 and a liquid level responsive control device 24 for turning the pump 22 on at a predetermined high sewage level and off at a predetermined low sewage level.

As shown, the air lift 22 comprises a vertical eductor pipe 26 of substantial diameter, for example 4 inches, mounted within the well and a compressed air supply pipe 28 communicating at one end with the eductor pipe 26 at a location near the lower end of the latter and below the lowest sewage level. The other end of the air supply pipe 28 connects with a source of compressed air, such as a blower 30.

The eductor pipe 26 is mounted within the well in a fixed position by any suitable means, such as a bracket 32 secured to the inner surface of the side wall 10. The upper end of the pipe 26 communicates by means of a fitting 34 with a laterally extending outlet pipe 36 which leads to another pumping station, 'or to a sewage treatment plant or other installation. The outlet pipe 36 is inclined slightly so that gravity flow of sewage takes place after the sewage enters the pipe 36 from the eductor pipe 26. In the construction shown the outlet pipe 36 is of larger diameter than the eductor pipe 26 and connection between the two is effected by means of a short length of pipe 38 extending horizontally from the fitting 34 into the end of the outlet pipe 36 and held in place by grout 40. The connection between the lower end portion of the eductor pipe 26 and the air pipe 28 is arranged so as to distribute the air into the pipe 26 in the form of many small bubbles. As shown, a vertical section of the pipe is perforated, as at 42, and the air pipe 28 is connected to an annular jacket 44 which surrounds the perforated section.

The air lift control 24 may be of any suitable type adapted for off-on control of the flow of compressed air in the air supply pipe 28. As shown, the control 24 includes a float 46 which rides on the surface of sewage 48 in the well and a sensor 50 for sensing the position of the float 46. When the float 46 reaches a predetermined high level, as shown in full line in FIGURE 1, the sensor 50 generates an electrical blower-on signal which is transmitted to the blower 30 by a control line 52. The dotted line position illustrates a predetermined low float level at which the sensor 50 generates a blower-off signal.

According to one of the features of the present invention the connection between the eductor pipe 26 and the air supply pipe 28 is located within a pipe 54 which extends downwardly into the earth from the deepest part of the well. The pipe 54 thereby forms a sump in which the depth of sewage is greater than the depth in the well by an amount equal to the length of the sump pipe 54. This extra depth contributes to the efficiency of the air lift 22, because by connecting the air supply pipe 28 to the eductor pipe 26 at a location within the sump pipe 54 a greater static pressure head exists in the eductor pipe 26 than would otherwise be present. This greater pressure is advantageous because it assures that the air lift 22 will operate at high capacity. An increase in the water pressure against which the air is introduced into an air lift increases the pumping capacity of the lift, because the pumping action of this type of pump is proportional to the pressure differential between the ends of the eductor pipe. Thus, in the absence of the sump pipe 54 there would be only slight pumping action at low sewage levels.

The length of the sump pipe 54 will vary with the type of installation. For many purposes it has been found that a length of as little as feet is adequate. The diameter must be sufiicient to permit the solids in sewage to pass downwardly between the outside of the eductor pipe 26 and the inside of the sump pipe 54. For a 4-inch outside diameter eductor pipe it has been found that a 16-inch outside diameter sump pipe is adequate.

According to another feature of the present invention a wet well or the like which includes a sump pipe as described above is constructed in an economical manner by first excavating for the well, then driving the sump pipe into the earth at the bottom of the excavated cavity and subsequently constructing the wet well above the sump pipe. In the preferred method of construction the sump pipe is jetted into the earth by water pressure thereby eliminating the additional excavating which would otherwise be necessary. This is accomplished most conveniently by means of a specially constructed sump pipe which includes a jet pipe or the like which in operation will loosen and flush away the earth from the lower end of the sump pipe thereby allowing it to burrow into the earth.

As best shown in FIGURE 2 the sump pipe 54 is adapted for jetting into the earth by means of two vertically extending jet pipes 56 which are attached to the outside of the sump pipe 54 as by welding. In addition the lower end of the sump pipe 54, which is closed by a plate 57, is provided with a cutter head 58 which penetrates the earth loosed by the water. The cutter head 58 may be conveniently constructed of triangular plates 60 welded along one edge to the lower surface of the plate 57 in a manner such that their apices coincide with the axis of the sump pipe 54. Each of the jet pipes 56 terminates at its lower end in a downwardly and inwardly facing nozzle 62 disposed adjacent the cutter head 58. The upper end of each jet pipe 56 terminates in a laterally extending portion 64 which is threaded at its end for connection to a flexible water conduit 66 (FIGURE 4).

In the illustrated embodiment the sump pipe 54 is also provided at its upper end with a bail 68 by means of which it may be manipulated during construction of a wet well. As shown, the bail 68 is an inverted generally U-shaped bar welded at each end portion to the exterior of the sump pipe 54. A ring-shaped disk 70 surrounds the sump pipe 54 and is welded thereto and to the ends of the bail 68.

FIGURES 4, 5 and 6 illustrate the preferred method of constructing the concrete wet Well shown in FIGURE 1. With respect to FIGURE 4 it is assumed that a cavity 72 has been excavated in the earth by any conventional technique. The cavity need be only as deep as the vertical dimension of the intended well exclusive of the length of the sump pipe 54. When the cavity 72 has been dug to the proper depth, one of the flexible hoses 66 is connected between the upper end of each jet pipe 56 and a source of water pressure, the latter being illustrated as a pump 74. Lifting and lowering equipment including a cable 76 is then attached to the bail 68, and the sump pipe 54 and water hoses 66 are lowered into the cavity 72. When the cutter head 58 reaches the bottom of the cavity 72, water is pumped into the jet pipes 56 and is discharged from the nozzles 62. As the earth is loosened and removed by the action of the cutter head 58 and the water flow a hole 78 is formed into which the sump pipe 54 is gradually lowered.

The jetting and seating of the sump pipe 54 are continued until only a minor proportion of the pipe 54 remains above the bottom of the cavity 72. Then the hoses 66 are disconnected, and the bail 68 is removed. Following this, as shown in FIGURE 5, the bottom wall 12 of the Well is constructed by casting a cement slab on the bottom of the cavity 72 in surrounding relationship to the portion of the sump pipe 54 which Was left exposed. In the method illustrated the jet pipes 56 are left in place and are therefore partially embedded in the concrete.

As shown in FIGURE 6 the side wall 10 of the well is then cast on top of the bottom wall 12 following which the remainder of the excavation is filled in. The casting operation will normally include the installation of the inlet pipe 20 and outlet pipe 36. The air lift 22 is then installed by assembling the eductor pipe 26, collar 44 and the lower section of the air supply pipe 28 and lowering the assembly downwardly through the open upper end of the well. The fitting 34 (FIGURE 1) is screwed on to the upper end of the eductor pipe 26 and the pipe 38 is slipped into the outlet pipe 36 and then screwed into the side of the fitting 34. A suitable number of brackets 32 are installed following which the remainder of the components shown in FIGURE 1 are installed in any suitable manner. v

In use of the well raw sewage flows in through the inlet pipe 20 until the level of sewage 48 raises the float 46 to the solid line position shown in FIGURE 1. A pump-on signal then passes from the sensor 50 to start operation of the blower 30. Compressed air passes through the pipe 28 and is discharged into the sewage in the eductor pipe 26 through the collar 44 and perforations 42. The air is distributed in the form of many small bubbles which lower the density of that portion of liquid and cause it to rise in the eductor pipe 26. This causes sewage to flow into the open lower end of the pipe 26 and out of the upper end into the outlet pipe 36. When the float 46 moves downwardly to the dotted line position, the sensor 50 stops operation of the blower 30.

As already indicated the entry of the air into the eductor pipe at a location well below the level of sewage 48 in the well assures that the air lift 22 will operate efliciently and with high capacity even at low sewage levels. The principles of operation of air lifts are well known and need not be described in detail except to point out that the pumping action increases with an increase in the head of liquid against which the air is forced into the eductor pipe. The present invention makes use of this feature by providing the sump pipe 54 which increases the effective depth of the well, and consequently the pumping capacity of the air lift, without increasing the actual vertical dimension of the well or the vertical dimension of the excavation. Therefore, even at the air cut-01f level of sewage there is a substantial head of liquid acting on the point of entry of air into the eductor pipe 26.

According to another feature of the invention the assembly of sump pipe 54, jet pipes 56 and cutter head 58 may be employed without a separate wet well above it. In such an arrangement the sump pipe 54 is of substantial length and extends to the surface of the ground and serves as its own wet well. The manner of jetting the assembly into the ground is the same as described above except that a wet-well cavity is not dug prior to the jetting step. Following installation of the assembly the air lift pipe 26 is lowered into place and fixed in position in any suitable manner.

It will be understood that the described embodiment is given by way of example and that the details thereof are not intended to be limiting except as they appear in the appended claims.

What is claimed is:

1. A method of constructing a liquid collecting and pumping station for liquid waste comprising: excavating a cavity in the earth of suflicient size to receive a container for liquid to be collected; providing a length of pipe of substantially lesser diameter than said cavity and having a closed lower end and an open upper end and forcing said length of pipe into the earth at the bottom of said cavity to a final position in which said open upper end is within the lower part of said cavity; installing a container in said cavity above said open end of said pipe and placing said open end in communication with the interior of said container through the bottom of said container; and lowering a vertically extending air lift pipe downwardly to a position in which the lower end of said air lift pipe projects into said length of pipe a substantial distance and fixing said air lift pipe in said position.

2. A method as in claim 1 wherein said containerinst-alling step includes casing cement on the bottom of said cavity and simultaneously around the exterior of said open upper end of said pipe thereby forming the bottom of the container.

3. A method as in claim 1 wherein the step of forcing said length of pipe into the earth at the bottom of the cavity includes providing said pipe exteriorly with fluid jet means and fluid supply conduits which terminate near the upper end of said pipe and jetting said pipe into the earth with fluid under pressure and wherein said cementcasting operation includes casing cement around the upper ends of said fluid supply pipe and subsequently casting cement walls on said container bottom to complete the container.

References Cited UNITED STATES PATENTS 661,623 11/1900 Shaw 103232 988,177 3/1911 Diebold 10'3232 1,024,821 4/1912 Bignell 422 X 1,356,646 10/1920 Maher 6l-53.74 1,529,112 3/1925 Burns 6153.74 2,354,936 8/1944 Bignell 61-53.74 2,427,157 9/1947 Piersol 103232 3,078,809 2/1963 Wakefield 103232 3,128,604 4/1964 Sandberg 61-53.74 X

EARL I. WITMER, Primary Examiner. 

